Ring laser gyros (RLGs) are instruments used to measure angular rotation. They include a cavity in which two laser beams travel in counter-rotating (i.e., opposite) directions. The laser beams create an optical interference pattern having characteristics representative of the amount by which the RLG is rotated. The interference pattern is detected and processed to provide the angular rotation measurements.
RLGs are subject to a phenomenon known as “lock-in” which can degrade their measurement accuracy. One known approach for minimizing lock-in is dithering. Dithering is the mechanical oscillation of the RLG. This function is provided by a dither system which includes a motor for generating the oscillations, and a transducer for generating a signal known as the dither pick-off which is representative of the dither motion amplitude and frequency. RLGs also typically include a path length control (PLC) system which adjusts the path length of the laser beams within the RLG cavity to maintain peak steady state intensity/power.